CA2146975A1 - Process for hydroxycarbonylating pentenoic acids - Google Patents

Abstract

A method for hydroxycarbonylating pentenoic acids, wherein one or more pentenoic acids are hydroxycarbonylated into adipic acid with carbon monoxide and water in the presence of an iridium and/or rhodium based catalyst and at least one iodated promoter; the resulting reaction mixture is refined, optionally after having been concentrated, to separate at least a portion of the catalyst; and the catalyst thus separated is recycled in a pentenoic acid, butadiene or butadiene derivative hydroxycarbonylation process.

Description

~ O 94/08939 21 ~ 6 9 7 5 PC ~ r / FR93 / 01028 PROCESS FOR HYDROXYCARBONYLATION OF PENTENOIC ACIDS

The present invention relates to a process for the hydroxycarbonylation of pentenolic acids for p, ~ pa, dlion of adipic acid, in the presence of a catalyst 5 which is at least partially separated from the reaction mixture obtained after the hydroxy-carbonylation and reused in a hydroxyca, l, onylation operation.
One of the most promising methods of prepardlion of adipic acid consists of hydroxycarbonylating one or more ~ Irs pentenoic acids, especially acid pentene-3-oic and pentene-4-oic acid, using carbon monoxide and water, 10 in the presence of a catalyst based on iridium, rhodium or their mixtures and a Iodine promoter Generally the reaction is carried out in the liquid phase at a temperature from 50C to 300C and under partial pressure of carbon monoxide from a few bars. To consider the industrial use of a process of this type, it is obviously essential to be able to recycle at least part of the costly catalyst used.
The present invention specifically relates to a method comprising a such recycling Among the possible lion separation techniques, the ~ I; s ~ lion des coi "posed the most volatile reaction mixture from hydroxyca, ~ onylation leaves 20 remain the catalyst with ~ ides formed A ~ isti "~ tion later of these ~ Low vapor pressure acids require that they and the catalyst be subjected to a prolonged heating at relatively high temperature, likely to degrade them and to make the catalyst partially or totalc. "enl inactive.
The tech ~ ue of crisl ~ '' isc ~ ion requires to ensure a thermal transfer 25 sufficient and to allow obtaining crystals of size required to be wrung. In in addition to the rate ", axi", al of solids is limited to a higher value of the order of 30 to 40% ~ All this leads to a volume of appar .. "~ ge i", pG, lanl and illlllloti ~; s ~ lioll of too much catalyst very expensive ~ nt.
The present invention proposes to solve the problem of separation and 30 of the recycling of the catalyst within the framework of a hydroxy ~ process, Lonylation of acids pentenols in adipic acid, by the use of lechn. ~ _e refining.
More particularly, the invention relates to a hydroxy-carbonylation of pentenoic acids, characterized in that:
- on hydroxycarbonyl one or more pentenolic acids in acid 3 ~ adipic, with carbon monoxide and water, in the presence of a catalyst based iridium eVou rhodium and at least one iodized promoter, WO 94/08939 5 2 PCr / FR93 / 01028

2 ~ 4 6 the reaction mixture obtained is subjected to a refining operation, after being possibly concentrated, allowing to separate at least a part catalyst, the catalyst thus separated is recycled in a hydroxy operation 5 carbonylation of pentenoic acids or butadiene or butadiene derivatives.

The term pentenoic acid is understood to mean, within the framework of the invention, pentene-2-oic acid, pentene-3-oic acid, pentene-4-oic acid and their mixtures.
Pentene-3-oic acid taken in isolation or as a mixture with its isomers 10 is more particularly suitable, because of its accesibility and the results satisfactory to which it leads during its hydroxycarbonylation.
The catalyst used for the hydroxycarbonylation reaction can be based on rhodium, iridium or these two metals Any source of rhodium or iridium is likely to be used 15 in use.
As examples of rhodium sources which can be used in particular ~ es ~
reference may be made to the compounds cited in European patent EP-A-0 477 112, the content is incorporated by reference into this patent application As examples of sources of iridium which can be used in particular, 20 can quote:
- Metallic ir; Ir 2; Ir2 3;
- Ir C13; Ir Cl3.3H2O;
- Ir Br3; Ir Br3.3H2O;
-Irl3 - Ir2 (CO) 4cl2; Ir2 (C) 412;
- Ir2 (cO) 8; Ir4 (CO) 1 2;
- Ir (CO) [P (C6H5) 3] 2 I;
- Ir (CO) [P (C6H5) 3] 2 Cl;
- Ir [P (C6H5) 3] 3 I;
- Hlr [P (C6H5) 3] 3 (CO);
- Ir (acac) (CO) 2;
- [IrCl (cod)] 2;
(cod = cyclooctadiene-1,5; acac = acetylacétona ~ e).

The iridium catalysts which are more particularly suitable are:
[IrCl (cod)] 2, Ir4 (CO) 12 and Ir (acac) (CO) 2.

~ 0 94/08939 21 ~ 6 9 7 $ PCr / FR93tO1028 Iridium-based or iridium-rhodium-based catalysts are particularly preferred in the context of the process of the invention.

The amount of catalyst to be used can vary within wide limits.
limits.
In general, an amount expressed in moles of metallic iridium eVou of metallic rhodium per liter of reaction mixture between 10-4 and 10 ~ 1 conduit has satisfactory results. Smaller quantities can be used:
observes, however, that the reaction speed is low. Higher quantities have disadvantages than economically.
Preferably the concentration of iridium eVou rhodium is between 5.10-4 and 10-2 mole / liter.
By pro "~ iodized engine means in the context of the process of the invention Hl and organo-iodine compounds capable of generating Hl under reaction conditions and more particularly the alkyl iodides having 1 to 10 carbon atoms. Iodide methyl is more particularly recommended.
The amount of iodinated promoter to be used is generally such that the molar ratio l / lr (and / or Rh) is greater than or equal to 0 1. It is not desirable that this ratio exceeds 20. Preferably the molar ratio l / lr (eVou Rh) is understood between 1 and 5.

The presence of water is essential for the conduct of the hydroxy-General carbonylation ", the quantity of water to be used is such that the water / pentenolic acid molar ratio is between 0 01 and 10.
More is not desirable due to loss of catalytic activity observed. The water / pentenolic acid molar ratio in the reaction mixture may be less than a minimum below the indicated value previously if you do it for example, continuous jection of water rather than its introduction with the other fillers before the hydroxycarbonylation reaction Preferably, the water / pentenolic acid molar ratio is co ", p, is between 0 01 and 1 the previous remark concei "ing the minimum value also being valid.

The reaction of hydroxy ~, L, onylation can be carried out either in a third solvent either in a strong excess of pentenoic acids.

9 7 ~ PCr / FR93 / 01028 H

As a third solvent, it is possible to use in particular carboxylic acids saturated or aromatic aliphatics with a maximum of 20 carbon atoms provided that they are liquid under the reaction conditions. As examples such carboxylic acids include acetic acid, propionic acid, acid butyric, valeric acid, adipic acid, benzoic acid and phenylacetic acid.
The third solvent can also be chosen from saturated hydrocarbons aliphatic or cycloaliphatic and their derivatives c: hirés and hyd ~ carbides aromatics and their chlorinated derivatives, provided that these compounds are liquid under the reaction conditions. As examples of such solvents, mention may be made of benzene, toluene, chlorobenzene, dichloromethane, hexane and cyclohexane.
When present in the reaction mixture, the third solvent represents for example from 10% to 99% by volume relative to the total volume of said mixture reaction and preferably from 30% to 90% by volume.
According to a preferred variant, the hydroxycarbonylation reaction is produced in the pentenoic acids themselves, that is to say the pentene-2-olque acid, Pentene-3-oic acid, pentene-4-oic acid and mixtures thereof.

The hydroxycarbonylation reaction is carried out under pressure higher than atmospheric pressure and in the presence of carbon monoxide. Can use substantially pure or technical grade carbon monoxide as it is commercially available.
The reaction is carried out in the liquid phase. The temperature is generally co ", pr, between 100C and 240C and preferably between 160C and 200C.
The total pressure can vary within wide limits. The partial pressure of the carbon monoxide, measured at 25C is generally 0.5 bar to 50 bar and ~ reference from 1 bar to 25 bars.

The reaction mixture resulting from the hydroxycdrL reaction, onylation comprises essentially pentenoic acids, not l, ar, sro "" és, water, pro "~ iodized olor, catalyst, the solvent optionally used, the adipic acid obtained, the others by-products consumed in more or less i ", po, lante quantities, such as acid 2-methylglutaric, 2-ethyl succinic acid, valeric acid or gamma-valerolactone (or 4-methyl butyrolactone).
This reaction mixture is subjected to a refining operation, such as which, preferably after an operation of concer, l, dlion, consisting in eliminating, in particular pa ml; s ~; llalion, part or all of the third solvent, if such a solvent has been Wo 94/08939 pcr / FR93 / olo28 used, or part of the excess pentenoic acids when the reaction has been carried out without third-party solvent. By such a concentration, the weight of the reaction mixture at a value representing from 10% to 90% of its initial weight, without these figures having a critical value.
Refining in this text is defined as direct crystallization reaction mixture, preferably concentrated, on a cooled wall, on which deposits the raffinate (essentially adipic acid), while the remaining liquid concentrated in the other constituents of the treated mixture, including the catalyst.
However the crystal lattice deposited retains by capillarity or inclusion a quantity limited residual liquid.
This technique is also known as crystallization in the melt.
In the context of the process of the invention, the main objective of refining is to separate most of the adipic acid from the remaining catalyst mainly in the liquid residue (racking); for this we choose a device having a high ratio of heat exchange area / volume of reaction mixture to be treated, so as to limit the duration of crist ~ is ~ tion of the raffinate and especially the stock of reaction mixture and allow a cry rate ~ lallisalion that can exceed 70%.

The refining operation can be described in the following general way The reaction mixture to be treated is introduced into the apparatus, at a initial temperature at least equal to the temperature of crist ~ s ~ tion of the mixture and, preferably, between this temperature and the temperature to which was driven the hydroxycarbonylation reaction; The device itself is also at this temperature This initial temperature is generally between 100C and 200C.
The first phase of the operation consisle in the crist ~ ll; s ~ progressive ion adipic acid on the walls of the device This crystallization is obtained by a proS ~, d ", l" ée decrease in the temperature of the heat exchange walls, in particular using a calopo fluid, circulating them on the other side of the ~ ites walls.
Depending on the type of industrial re ~ iis ~ lion envisaged, the decrease in - temperature can be more or less rapid, depending on whether the mixture to be treated crystallizes in a relatively thin layer when it does not fill the entire volume of the device, or that it crystallizes by forming a thick layer when the charged mixture is stationary 35 and fills the entire volume of the device.

WO 94/08939 PCr / FR93 / 01028 21d ~ 697 ~ 6 The final temperature reached is limited by the melting temperature of the eutectics of the various constituents of the reaction mixture. She will be chosen in depending on the composition of the reaction mixture to be refined and the amount of acid adipic that we want to crystallize. Generally, the higher this temperature will be 5 low, plus certain other constituents of the reaction mixture can contaminate the adipic acid crystals; conversely, the higher this temperature, the higher the rate of recovery of adipic acid in the raffinate will be low.
Taking into account the above, the final temperature is generally fixed between 0C and 70C.
When the chosen final temperature is reached, it is recovered by casting at the lower part of the apparatus, the draining fraction, enriched in catalyst and depleted in adipic acid compared to the reaction mixture treated. This constitutes the draining phase.
The third phase of the refining operation consists in carrying out a washing 15 crystals deposited on the walls of the apparatus, so as to recover the major part of the drip liquid still retained on said cries ~ aux. It is carried out in heating, at a variable speed depending on the type of industrial production, the crystals deposited, which causes their partial fusion; so there is drainage and the replacement on the crystals of the dlégoutt ~ ge liquid with a much richer liquid 20 in adipic acid. This phase is called penetrant phase Its importance quanliLali ~ re depends on the amount of catalyst that we want to recover etcondilionne the purity and the recovery rate of adipic acid. The fraction of sweating can be added to the fraction obtained during the draining phase or subjected to another operation of separation of its constituents by any technique, 25 in particular by refining.
The term racking designates in this text the part of the mixture separate reaction during the draining phase and / or the penetrant phase The temperature to which the raffinate is brought during the penetrant phase varies according to the quantity of catalyst which one wishes to react or the quantity of acid 30 purified adipic which one wishes to obtain This temperature is generally between the final temperature of the draining phase and 150C Preferably it is between 100C and 145C.
The raffinate deposited on the walls of the appliance can then be recovered ~
35 by rapid melting of the crystals.

~ WO 94/08939 2 1 4 6 9 7 S PCI / FR93 / 01028 The duration of the refining cycle, made up of these different phases, can vary from approximately 1 hour to 30 hours, depending on the industrial technology adopted; so a dynamic thin film system, offering a large heat exchange surface in relation to the volume to be treated, will require a much shorter duration than 5 thick-film static system.
Withdrawal, containing at least part of the catalyst, of the promoter iodized, unprocessed pentenoic acids as well as more or less i ", po, lantes of the various constituents of the reaction mixture treated, can be directly recycled in a hydroxyca reaction, bonylation (l ~ old ~ ent the fraction 10 éouKage), or be pre ~ l ~ hlement subject to one or more operations of separation, aimed at separating the catalyst from all or part of the other constituents (in particular the penetrant fraction). This additional separation can itself be produced by the refining technique; but it can be done by any other conventional technique, such as for example crystallization, distillation, extraction.
The raffinate, containing in addition, adipic acid and catalyst and more or less significant amounts of difrer ~ n ~ s constituents of the mixture reaction process, can itself be subjected to one or more operations additional separation, in order to separate the catalyst and the iodine promoter which it 20 contains As indicated previously for racking, this separation additional can itself be achieved by the refining technique; but she can be carried out by any other conventional technique, such as for example crist ~ l 's ~ tion, ~ is ~ lion, extraction. The catalyst and the pro ", iodized engine thus separated can then possibly be recycled.
The refining is carried out in such a way that at least 40% of the catalyst present in the reaction mixture to be treated and preferably at least 8Q%.
A preferred mode of the invention consists in carrying out an operation of 30 refining, during which at least 80% of the catalyst is separated, between a initial temperature between 100C and 200C and a final temperature for - draining phase between 20C and 60C, the temperature then being ~ e ", onlée between 100C and 145C for the ressu ~ ge phase; this refining operation is optionally followed by one or more ~ rs other operations, separation alions carried out on 35 some or all of the fractions obtained, to separate the rest of the catalyst from a part and at least some of the branched ~ i- ^ ides on the other hand The catalyst thus obtained during refining is recycled in the reaction of hydroxyc ~, L, o "ylation.

wo 94'029 ~ 94 6 9 ~ ~ PCI` / FR93 / 01028 ~

When the catalyst separated by the refining operation is used to the hydroxycarbonylation of butadiene or its derivatives, we will use example the technique described for rhodium in patents EP-A-0405433 or EP-A-0274076.
Besides butadiene, its most generally usable derivatives are:

3-butene-2-ol, 2-butene-1-ol, their mixtures and their carboxylic esters, including acetates, propionates, valerates, adipates and pentenoates The following examples illustrate the invention EXAMPLE 1 Hydroxycarbonylation of pentene-3-oic acid In an autoclave with agitation by self-aspirating turbine, cnte, we introduce:
- 2.45 9 (7.3 mmol) of lr in the form of [IrCl (cod)] 2 (3.3 mmol / l of reaction mixture)

- 4.17 9 (18.6 mmol) of Hl in the form of a solution aqueous at 57% by weight by weight (8.4 mmoUI) - 177.8 9 (9.9 mol) of water (4.5 mmol / l) - 2084 9 (20.84 mol) of pentene-3-oic acid (P3).

The autoclave, connected to the pressurized gas supply, is closed hermetically We admit cold 2 bar (0.2 MPa) of CO and heat to 185C in 20 min via an electric heating collar ~ When this temperature is aKeinte, the pressure is regulated to 20 bar (2 MPa).
We follow the kinetics of the reaction, by the absso ", lion of CO in a reserve connected to the reactor, the p, ~ ssion in the autoclave remaining constant.
After a reaction time of 30 min, cost "sponda,) l at consG" ~, nation total of the water introduced, the reaction is stopped by, ~ r, oiJiss ~ nl the reaction mixture.
The autoclave is degassed and the reaction mixture is drawn off in the liquid state at 120C
The reaction mixture is analyzed by vapor phase chromatography and by chro ", high liquid atography pe, rol", ance The following results are obtained:

~ WO 94/08939 214 6 9 7 S PCI '/ FR93 / 01028 - transformation rate (TT) of P3: 51%
- molar yield with respect to transformed P3 (RT), in adipic acid (A1): 65%
- RT in methylglutaric acid (A2): 11%
- RT in ethyl succinic acid (A3): 3%
- RT in gamma-valerolactone (VAL): 11%
- RT in valeric acid (Pa): 2%
- RT in pentene-2-oic acid (P2): 8%

The linearity rate, expressed as the percentage ratio of A1 formed over the total of the diacids A1, A2 and A3 formed is 82%
The reaction speed (calc ~ lated over 20 min of abs "uLion of CO) is ~, 4 moles of CO absorbed per hour and per liter of reaction mixture.
The reaction mixture is concentrated by dislill ~ lion volatile products to 90C, under a pressure of 1 kPa; a mixture is thus obtained which is subjected to a refining operation.

EXAMPLE 2 - Raffnaqe of the reaction mixture concenl, ~ prepared in Example 1 The device used consists of a metal cylinder, dia ", èl, ~ interior 45 mm and height 65 cm, closed at its base by a pneumatic valve of small volume and provided at its ~. top with a screwed cover crossed by two probes temperature and a nitrogen supply.
The whole is surrounded by a double envelope allowing circulation organized with a calGpo fluid, their temperature controlled.
1058 9 of concentrated reaction mixture prepared in Example 1 and having the following weight composition:

- adipic acid 66.00%
- methyl-2-glutaric acid 11.20%
- ethyl-2-succinic acid 2.00%
- g ~ r "", a-valerolactone 1.80%
- pentene-2-oic acid 3.00%
- pentene-3-oic acid 14.50%
- pentene-4-oic acid 1.30%
- iridium (metal) 0.0887%
- iodine 0.1565%

WO 94/08939 PCr / FR93 / 01028 ~
21 ~ 97 5 10 This reaction mixture in the liquid state at 131C is loaded into the apparatus.
being at this same temperature.
The temperature is gradually lowered using the coolant up to 40C in 9 h: this is the crystallization phase.
At 40C, the device valve is open and the draining phase is carried out at constant temperature for 3 h: the drip fraction is thus recovered representing by weight by weight 20% of the loaded reaction mixture.
The temperature then gradually increased to 138C in 11 hours;
during this PT phase, a PT fraction representing 10 by weight by weight 28% of the charged reaction mixture.
Finally the temperature is brought in 3 hours to the melting temperature of the raffinate deposited on the walls of the device and is maintained at this temperature for another hour. The raffinate is thus recovered, which represents 52% by weight by weight of the charged reaction mixture.
By dosing by g-phase chromatography ~ Puse, by chromatography high performance liquid and by X fluorescence, the compositions are determined respective of these three fractions.

Sewage fraction:
- adipic acid 10.0%
- methyl-2-glutaric acid 32.0%
- ethyl-2-succinic acid 5.4%
- gamma-valerolactone 8.4%
- pentene-2-olque acid 7.9%
- pentene-3-oic acid 33.5%
- pentene-4-olque acid 2.5%
- iridium (metal) 0.210%
- iodine 0 370%
Spring fraction:

- adipic acid 48.0%
- methyl-2-glutaric acid 19.5%
- ethyl-2-succinic acid 3.3% ~
- gamma-valerolactone 4.8%
- pentene-2-oic acid 5.5%

~ VO 94/08939 21 ~ 6 9 7 S PCI` / FR93 / 01028 - pentene-3-oic acid 18.5%
- pentene-4-oic acid 0%
- iridium (metal) 0.133%
- iodine 0.228%
RaKinat:

- adipic acid 95.8%
- methyl-2-glutaric acid 2.2%
- ethyl-2-succinic acid 0%
- gamma-valerolactone 0%
- pentene-2-oic acid 0%
- pentene-3-oic acid 2.0%
- pentene-4-oic acid 0%
- iridium (metal) 0.0149%
- iodine 0.0264%

The raffinate therefore contains 76% of adipic acid and only 9% of the iridium and iodine present in the reaction mixture resulting from the reaction Hydroxycarl, onylation.
The draining fraction contains 45% of iridium and iodine and 3% of adipic acid from the reaction mixture, while the PT fraction contains 46% of iridium and iodine and 21% of adipic acid ~ lobAIe ~ ent the racking consisting of all the draining and bleeding fractions therefore contains 91%
25 iridium and iodine with 24% adipic acid from the reaction mixture. Of pa, different lages of the fractions and the raffinate allow either to "~ inil" iser the quantity adipic acid present in the racking, i.e. to increase the recovery rate of iridium and iodine according to the preferred separation criterion.

EXAMPLE 3 - RecYclaqe in a reaction of HydroxYca, Lo "~ lation de la ~ ion of sewage obtained in example 2 100 9 of the r is recycled (sewer acLion ~ ge obtained in Example 2.
add pentene-3-oic acid and water to it, so as to have an initial reaction mixture having the same concentration in Ir and in Hl as the initial mixture used in Example 1, that is to say 3.3 mmol / l of lr and 8.5 mmol / l of Hl.

WO 94/08939 ~ ~ 9, ~ ~ 12 PCr / FR93 / 01028 The concentrations of the initial mixture for the other constituents are the following:

- 7 mmol / l of P3 - 0.2 mmol / l of P2 - 0.04 mmol / l P4 - 0.24 mmol / l of VAL
- 0.18 mmol / l of A1 - 0.6 mmol / l of A2 - 0.1 mmol / l of A3 - 4.2 mmol / l of water.

The hydroxycarbonylation is carried out as described in Example 1. After 40 min of reaction, corresponding to the consumption of the water introduced, it is cooled 15 in the autoclave and the various constituents of the final reaction mixture are assayed.

We obtain the following results ~ tc:

- rate of ll dnsrol ,,, alion (TT) of P3: 58%
- RT in adipic acid (A1): 65%
- RT in methylglutaric acid (A2): 13%
- RT in ethyl succinic acid (A3): 3%
- RT in gamma-valerola ~ lone (VAL): 9%
- RT in valeric acid (Pa): 3%
- RT in pentene-2-oic acid (P2): 7%

The linearity rate, expressed as the percentage ratio of A1 formed over the total of the diacids A1, A2 and A3 formed is 80%.

The reaction speed (c ~ c ~ '~ e over 20 min of CO abso "lion) is 4.4 moles of CO absorbed per hour and per liter of reaction mixture. Kinetics being of order 1 with respect to P3, there is therefore an activity of the catalyst identical to that observed in Example 1 (volume abso "~ lion of CO / quantity of P3 involved).

Claims (15)

1) Process for the hydroxycarbonylation of pentenoic acids, characterized in that that :

- one or more pentenoic acids are hydroxycarbonylated into acid adipic by carbon monoxide and water, in the presence of a catalyst based on iridium and/or rhodium and at least one iodinated promoter, - the reaction mixture obtained is subjected to a refining operation, optionally after having been concentrated, making it possible to separate at least a part catalyst, - the catalyst thus separated is recycled in a hydroxy-carbonylation of pentenoic acids. 2) Process for the hydroxycarbonylation of pentenoic acids, characterized in that that:

- one or more pentenoic acids are hydroxycarbonylated into acid adipic by carbon monoxide and water, in the presence of a catalyst based on iridium and/or rhodium and at least one iodinated promoter, - the reaction mixture obtained is subjected to a refining operation, optionally after having been concentrated, making it possible to separate at least a part catalyst, - the catalyst thus separated is recycled in a hydroxy-carbonylation of butadiene and/or its derivatives. 3) Method according to one of claims 1 or 2, characterized in that one separates by the refining operation at least 40% of the weight of the catalyst contained in the reaction mixture and preferably at least 80%. 4) Method according to one of claims 1 or 2, characterized in that the reaction mixture obtained after the hydroxycarbonylation operation is concentrated before being subjected to the refining operation to eliminate at least part of the the most volatile compounds it contains. 5) Process according to claim 4, characterized in that the concentrate of reaction mixture subjected to the refining operation represents by weight per weight of 10% to 90% of the reaction mixture resulting from the hydroxycarbonylation operation. 6) Method according to one of claims 1 to 5, characterized in that the hydroxycarbonylation is carried out in a solvent chosen from acids carboxylic acids such as saturated aliphatic acids and aromatic acids having less than 20 carbon atoms, saturated aliphatic hydrocarbons or cycloaliphal compounds and their halogenated derivatives, aromatic hydrocarbons and their halogenated derivatives and aliphatic, aromatic or mixed ethers 7) Method according to one of claims 1 to 5, characterized in that hydroxycarbonylation is carried out in the pentenoic acids themselves 8) Method according to one of claims 1 to 7, characterized in that the refining consists of cooling the mixture in a controlled and progressive manner reaction, optionally concentrated, from an initial temperature at least equal to the crystallization temperature of the mixture and, preferably, between this temperature and the temperature at which the reaction of hydroxy-carbonylation to a final temperature greater than or equal to the melting point of the eutectic of the constituents of said reaction mixture, so as to crystallize gradually adipic acid from the reaction mixture. 9) Process according to claim 8, characterized in that the temperature initial is between 100°C and 200°C and the final temperature between 0°C and 70°C. 10) Method according to one of claims 1, 2, 8 and 9, characterized in that that refining includes a second phase, or draining phase, making it possible to separating at least a portion of the catalyst within a drain fraction 11) Method according to one of claims 1, 2, 8 to 10; characterized in that that refining includes a third phase, or sweating phase, consisting, for progressive heating of the crystals deposited, to recover a bleeding fraction containing another part of the catalyst as well as other constituents of the mixture treated reaction. 12) Process according to claim 11 characterized in that the phase of Penetrant testing is carried out by heating to a temperature between the temperature end of the draining phase and 150°C and preferably between 100°C and 145°C. 13) Method according to one of claims 1, 2 and 8 to 12 characterized in that that the duration of the refining cycle varies between 1 hour and 30 hours. 14) Method according to one of claims 1, 2 and 8 to 13 characterized in that that the fraction obtained in the draining phase is recycled in the reaction of hydroxycarbonylation. 15) Method according to one of claims 1, 2 and 8 to 13 characterized in that that the fractions obtained in the draining and sweating phases are recycled in the hydroxycarbonylation reaction.